1. Field of the Invention
The present disclosure generally relates to a wireless multi-functional sensor platform, a sensor system containing same and method for its use. More particularly, the present disclosure is directed to an in-situ multi-functional sensor system containing a plurality of wireless multi-functional sensor platforms and method for providing long-term monitoring of various parameters associated with a medium, e.g., concrete, by embedding the sensor system within the medium to predict the onset of degradation and thus aid in the scheduling of maintenance, management and repair thereof.
2. Description of the Related Art
In the United States, billions of dollars have been spent in the construction of highways, freeways and their associated overpasses, bridges and buildings. One of the most important problems facing the nation is determining how to maintain the integrity of this system of roads and other structures at an acceptable cost. Obviously, it would be advantageous for practitioners in the art to have the benefit of a permanent, early-warning system for detecting structural degradation in the earliest stages.
One of the primary applications of this technology is in the area of bridge-deck monitoring. Currently, bridge deck monitoring is based on individual sensor measurements or periodic visual inspection by trained personnel. This approach doesn""t detect bridge deck or foundation degradation until it has already reached an advanced state. By this time, remedial actions are more expensive than if the problem had been detected earlier. In addition, significant degradation impacts repair schedules and quality of service for the bridge.
Yet another problem associated with present day sensor systems for use in bridge monitoring is that the sensors are not distributed throughout the bridge deck. Instead, they are used only for discrete measurements, mostly due to economic limitations. Furthermore, the cost of making measurements employing present day technology is high due to installation and monitoring requirements.
Further problems associated with prior art solutions for bridge monitoring is that recent research has focused on mechanical sensing such as stress/strain and pressure. Sensors that are being designed to address corrosion-related degradation are limited to specific parameters such as, for example, chloride and temperature, or gross measurements of physical properties such as conductivity.
Thus, it would be particularly advantageous to employ sensors which measure a multitude of parameters for various mediums that extend beyond those described above. Such parameters may include those related to the structural, chemical and/or environmental conditions associated with a medium such as, for example, magnetism, noise, pH, pressure, shock, strain, stress and vibration. Accordingly, a need exists for a multi-functional sensor system for providing long-term monitoring of a plurality of parameters of a medium to preemptively detect the onset and degree of degradation. In this manner, protective measures can be promptly taken to ensure that the medium is properly maintained.
It is an object of the present invention to provide an early-warning multi-functional sensor system for monitoring a plurality of parameters, e.g., structural, chemical and/or environmental conditions, associated with a medium such that the onset of degradation can be detected employing the multi-functional sensor system.
It is a further object of the present invention to provide an early-warning multi-functional sensor system that may be embedded in a medium such as, for example, concrete buildings, bridges or in contaminated ground zones, for long-term monitoring of the medium to both detect the onset of degradation and to prevent or forestall further degradation.
Yet another object of the present invention is to provide a plurality of wireless multi-functional sensor platforms for use in the early-warning sensor system that are compact in size, relatively low in cost and are capable of being remotely powered to facilitate their long term use such that numerous sensors may be used in a single project, e.g., embedded in a reinforced concrete bridge. The sensor platforms are designed to be powered and queried remotely as often as required for use in measuring a plurality of parameters of the medium in which they are embedded.
A further object of the present invention is to provide a plurality of wireless multi-functional sensor platforms that are capable of monitoring the medium in a nondestructive manner.
It is a further object of the present invention to provide a plurality of wireless multi-functional sensor platforms which may serve as an attachment base for supporting a plurality of sensor types on each platform specifically selected for use in monitoring a particular parameter associated with the medium to which the sensor platforms are embedded in.
It is yet a further object of the present invention to provide a plurality of wireless multi-functional sensor platforms that exhibit extremely high reliability for a prolonged period, e.g., on the order of several decades.
In keeping with these and other objects of the present invention, an early-warning multi-functional sensor system and method for using same are provided which includes a network of cost-effective, embeddable, remotely powered, ultra-small, ruggedized and long-lasting wireless multi-functional sensor platforms that are impervious to harsh environmental conditions such as salt, mechanical and thermal stress. The sensor platforms are particularly suited for long-term field measurements of parameters in a harsh environment. The sensor platforms are preferably constructed from a housing material that is of low cost and requires only standard automated machining, e.g., a ceramic material.
Accordingly, the sensor platforms are multi-functional in that they serve as platforms for attaching a multitude of sensor types (e.g., temperature, conductivity, pressure, pH, etc.) thereto for monitoring various parameters specific to the medium to be monitored. This capability of interchanging sensor types dependent upon the particular medium makes the sensor system of the present invention suitable for use in a wide variety of monitoring situations. Thus, when the platforms are employed in the sensor system, sensor platforms having a plurality of sensor types attached thereto are distributed throughout the medium to be monitored to acquire data directed to, for example, structural, chemical and environmental data, associated with the medium. The sensor system therefore advantageously provides an early warning indication of the present state of the monitored medium to aid in the medium""s timely maintenance and/or repair.
According to one aspect of the present invention, the operation of the sensor system includes disposing a plurality or network of wireless multi-functional-sensor platforms throughout a medium or zone in the medium to be monitored, with each of the sensors generating an output. Sensor data can then be collected periodically, via wireless means, which may be combined with historical data for analysis to ascertain the health of the medium.
Data collection is performed by an interrogation unit operable to generate power to and receive responses from the plurality of sensor platforms. In this regard, the data is collected in a non-invasive manner without impact on the medium being monitored.
In one exemplary application, the system of the invention involves distributing the wireless multi-functional sensor platforms approximately every two meters throughout a medium during or after construction. Periodically, a field data acquisition system passes over the network of sensors to infer the sub-surface environment. The resulting data is then used to forecast potential problem regions within the medium and measure the evolution of the structural, chemical and environmental parameters of the medium over time. As such, the sensor system provides an early warning indication of potential and ongoing adverse structural, chemical and environmental changes within the medium.
Other objects and advantages of the present invention will become more fully apparent from the following, more detailed description and the appended drawings, which illustrate several embodiments of the invention.